(a) Field of the Invention
The present invention relates to a temperature sensor for a display device, a thin film transistor array panel including the temperature sensor, and a liquid crystal display.
(b) Description of Related Art
Display devices used for monitors of computers and television sets generally include self-emitting display devices and non-emitting display devices. Self-emitting display devices include organic light emitting displays (OLEDs), vacuum fluorescent displays (VFDs), field emission displays (FEDs), and plasma panel displays (PDPs), and non-emitting display devices include liquid crystal displays (LCDs). Unlike self-emitting display devices, non-emitting display devices require a light source to display images.
An LCD includes two panels provided with field-generating electrodes that have a liquid crystal (LC) layer having dielectric anisotropy interposed between them. The field-generating electrodes are supplied with electric voltages to generate an electric field across the LC layer. Light transmittance through the liquid crystal layer varies depending on the strength of the generated electric field, which can be controlled by the applied voltages. Accordingly, desired images are displayed by adjusting the applied voltages.
The light source for an LCD may be lamps that are coupled to the LCD, or it may be an ambient light source such as the sun.
Since optical characteristics of the liquid crystal of the LC layer change based on temperature, the temperature variation of the LCD affects the reliability of the LCD. For example, optical characteristics such as refractive index, dielectric constant, coefficient of elasticity, and viscosity of the liquid crystal are inversely proportional to the thermal energy of liquid crystal molecules, and their values decrease as the temperature of the liquid crystal rises.
Operational characteristics of elements that are mounted on or integrated with the LCD also change with temperature.
A temperature sensor is disposed on a printed circuit board (PCB) mounted with a plurality of driving circuits to detect the temperature of the LCD. However, the PCB is generally disposed on the rear side of the LCD on which the lamps and any other heat-generating elements are disposed. The temperature sensor is not disposed on the front side of the LCD where the LC layer is formed. Thus, the temperature sensor detects the temperature at the rear of the LCD where temperature swings are large. The temperature that is detected by the temperature sensor may be significantly different from the temperature of the LC layer, and temperature compensation of the LCD based on the temperature at the rear of the LC layer is not precise.
Another disadvantage with the above-described configuration is that the temperature sensor is separately installed on the PCB. This separate installation increases design redundancy of the LCD, increasing manufacturing cost.